Reinforced structures incorporating strip deck material

ABSTRACT

A reinforced structure using settable material such as concrete to form a slab comprises a plurality of spaced, parallel loadbearing duct members of closed cross-section extending over and between at least two support surfaces of the structure and supported therefrom by a shear-resisting connecting means to constitute beam members. A thin strip extends beneath the duct members spaced therefrom and is connected to the duct members by shear-resisting connecting means, the strip serving as formwork for the layer of settable material while it is being poured, and reinforcement after it has set. The duct members and connecting means are completely embedded by the set material which enters the space between the strip and the duct members to provide a void-free layer between them. The duct members provide steel reinforcement for the set slab and also can constitute conduits or raceways for the provision of services through the resulting structure.

[4 1 July 15,1975

United States Patent 1191 Parazader 783.64l 9/1957 UnitedKingdom...........ln...v 52/469 REINFORCED STRUCTURES INCORPORATINGSTRIP DECK MATERIAL Primary E.mminerAlfred C. Perham Attorney, Agent, orFirmStanley 1. Rogers V A a n mo ea hd wm so V I M 7 [22] Filed: Aug. 301974 [2]] Appl. No.: 502,245

Related U.S. Application Data parallel load-bearing duct members ofclosed [63] Continuatiomin-part of Ser. No. 295.025, Oct. 4,

1972, abandoned, which is a continuation-in-part of cross-sectionextending over and between at least two Ser No. I51

,340. June 9. l97l. abandoned.

support surfaces of the structure and supported therefrom by ashear-resisting connecting means to consti- [52] U.S. Cl. 52/173;52/220; 52/335;

tute beam members. A thin strip extends beneath the 52/629 duct membersspaced therefrom and is connected to E04f 17/08 the duct members byshear-resisting connecting means, the strip serving as formwork for thelayer of settable material while it is being poured, and reinc r a e S t0 M .W F

forcement after it has set. The duct members and connecting means arecompletely embedded by the set material which enters the space betweenthe strip and the duct members to provide a void-free layer betweenthem. The duct members provide steel reinforcement for the set slab andalso can constitute conx m m E: 0 mm MA "H .lP m C s d mTmm m rTka mSRHD man '99 www 72 47 ll 6 l 5 mm Young FOREIGN PATENTS OR APPLICATIONSduits or raceways for the provision of services through the resultingstructure.

52/220 12 Claims, 13 Drawing Figures SHEET FIG. 5

FIG. 4

FIG. 3

SHEET FIG. ll

z 202/3 FIG. 8 Zia FIG. 9

FIG. T

FIG

SHEET FIG. 13

REINFORCED STRUCTURES INCORPORATING STRIP DECK MATERIAL CROSS REFERENCETO RELATED APPLICATION This application is a continuation-in-part of myapplication Ser. No. 295,025, filed Oct. 4, l972 now abandoned, which isin turn a continuation-in-part of my application Ser. No. l5 1 ,340,filed June 9, 1971 now abandoned.

FIELD OF THE INVENTION This invention is concerned with improvements inor relating to reinforced structures incorporating preformed strip deckmaterial.

REVIEW OF THE PRIOR ART One of the commonest forms of reinforcedstructure now built comprises a sectional steel deck which is placed inposition on a supporting steel framework, and over which a layer ofconcrete is applied. The set concrete and the steel deck co-operatetogether in what is known as composite action" to provide a floorstructure for the space above and a ceiling structure for the spacebelow. Designers now require the use of longer spans in order to obtainunobstructed floor space. The stronger steels and concretes nowavailable assist in meeting this requirement, but it has also provenpossible, by careful design of the deck material and the structureincorporating it, to provide a stiffer floor structure without reducingthe total slab thickness, or conversely to provide the same stiffness bythe use of a thinner floor slab. A stiffer slab will usually permit areduction in the weight of the supporting steel framework and may alsoresult in a reduction in the overall depth of the floor structure. Thesefactors become important in multi-storey buildings, in that it may bepossible to provide an additional storey of leasable space in astructure of given height.

Another important factor in the economical production of reinforcedstructures is whenever possible the reduction in the amount ofrelatively expensive, uncertain and inefficient field labour required,as compared with the amount of less expensive more efficient and easilycontrollable shop labour.

It is usually essential, especially in multi-storey structures, toprovide service ducts or raceways in the floor or ceiling structure,through which the various services such as electricity, telephone,intercommunication, heating, air-conditioning, water, can be suppliedand can be easily changed as occupancy of the building changes, or aschanges are made in a particular area of the building. These servicesusually should be readily accessible from above, particularly inoffice-type buildings, so that the occupant can make any necessarychanges without the need to enter the floor directly below. It is alsoof course necessary that the structure meet the minimum fire ratingrequirements of the appropriate authority.

An example of a way in which raceways have been provided is shown in US.Pat. No. 2,131,652, issued Sept. 27, l938 to H. H. Robertson Co., thefloor structures shown therein comprising a substantially flat lowermetal sheet over which is laid a corrugated upper metal sheet, with theoverlaid sheets resting on suitable supporting members. The uppercorrugations of the corrugated metal sheet are filled with concrete andform ribs on the underside of the resulting concrete slab, the sheetsproviding a permanent form upon which the concrete may be poured. Theflat metal sheet co-operates with the lower corrugations to close themand thereby form the service ducts, the sheet also forming a ceilingplate which provides the space below with substantially flat metalceiling which can be finished. The ducts may be entered from abovethrough holes or openings drilled through the concrete or they may beentered from below through the ceiling sheets.

British Pat. No. 748,104, published Apr. I8, 1956, and issued to thePre-stressed Concrete Company Limited, discloses building structures inwhich a preformed, pre-stressed plank is used for the subsequent castingin situ of floors or roofs. A plank is made by pouring concrete over aform consisting of mesh fabric, such as expanded metal, on which meshfabric ducts are laid, or alternatively in which ducts have been formedintegrally by bending up from the mesh fabric material. It is essentialtherefore for operation of this invention that the form is temporarilysupported during its production prior to setting of the concrete, sinceit is inherently not self-supporting. The ducts are intended principallyfor the accommodation of prestressing cables, although the specificationstates at page 1, lines -88 that if all the ducts are not required forcables they provide convenient passages through which services can berun. When the ducts are separate from the mesh sheet they may be weldedor wired thereto in well known manner and, in effect, also act asstiffening ribs for the mesh. It is intended that the concrete shallpenetrate the mesh so that the ducts and mesh act as a reinforcement forthe resultant plank. The specification states at page 1, lines 59-66that if additional reinforcement is required transversely to thedirection of the ducts, further ducts may be laid across those alreadyin position and the concrete either poured over both sets of ducts atonce or in two stages. These ducts, if provided, are therefore operativeas tensile reinforcement for the slab, and there is no disclosure orteaching of these ducts provided in a manner such that they can operateas beam members resisting both compression and tensile forces. It willbe seen that, if such further ducts are provided, the firstmentionedducts constitute large voids interposed between the mesh and the furtherducts. Moreover, the common method in the art of fastening additionalreinforcement to a primary reinforcement is by means of wires, whichtype of connection is inherently not shear resisting; there is thereforeno disclosure or teaching whatsoever ofa shear-resisting connectionbetween the first-mentioned ducts and said further ducts, if provided.

DEFINITION OF THE INVENTION In accordance with the present inventionthere is provided a reinforced structure comprising a support structureproviding at least two spaced support surfaces, a plurality of parallel,spaced, elongated, loadbearing duct members of closed cross-sectionextending between the said spaced support surfaces and over at least aportion of each of the said surfaces, shearresisting connecting meansdisposed between each support surface and the respective portion of eachduct member extending thereover, whereby each duct member constitutes abeam member supported by the support surfaces, void-free shear-resistingconnecting means connected to the duct members between the said portionswhich extend over the surfaces, a thin continuous strip extendingbeneath and spaced from the duct members over the space between thespaced support surfaces, and connected to the last-mentioned connectingmeans to be supported from the duct member to constitute formwork for asuperimposed layer of settable material and reinforcement for the layerwhen set, and a void-free layer of set material that has been set on thestrip as formwork therefor, the layer enclosing the duct members, theconnecting means and filling the spaces between the strip and theundersides of the ducts.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view from aboveillustrating a particular preferred example of a single span of my newdeck in roll form, being unrolled on to a support structure for theformation of a composite reinforced concrete floor/ceiling,

FIG. 2 is a similar view to FIG. 1, showing a multiple span rollabledeck being unrolled on to a corresponding support structure,

FIGS. 3 to 6 and 8 are similar views to FIG. I, of a small portionthereof, to illustrate different forms of fastening means for fasteningthe duct members to the strip material,

FIGS. 7 and 9 are sections taken on the lines 7-7 and 99 respectively ofFIGS. 6 and 8,

FIG. 10 is a section taken on the line I10 of FIG. 1 and showing thecross-section through a typical completed floor,

FIG. I I is a section similar to FIG. showing a mod ified form offastening means,

FIG. I2 is a perspective view similar to FIGS. 1 and 2 of anotherpreferred example wherein the sections of deck are placed on the supportstructure in flat form, and

FIG. 13 is a perspective view of a preferred example of deck asillustrated by FIG. 12, showing a modified form of raceway andillustrating the way in which the raceways are enclosed by the concrete.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now especially toFIGS. 1 and 2, in the particular construction shown therein theresulting composite floor/ceiling is supported by spaced primaryload-bearing members 12 (only one of which is shown), which in thisembodiment comprise spaced I-beams. In other embodiments other forms ofprimary members can be used, such as spaced pillars or columns, wallsand trusses. A plurality ofjoist or truss members 13 are supported attheir ends by the primary members 12 in generally horizontal spacedparallel relation to one another, the upper flanges of these joistmembers providing respective substantially flat uninterrupted uppermostsurfaces longitudinally of the joist members. Other forms of secondaryjoist members providing such an uppermost surface can of course be used.

Each joist 13 may in some examples be provided, by means of apreliminary shop operation under controlled conditions, with a pluralityof upwardlyprojecting shear connector members 16 disposed in spaceddistribution along the length of its surface 15. In this particularembodiment the connectors are illustrated as headed studs which arewelded to the upper chord of the joist, the studs being staggered inrelation to the joist centre line to avoid the junction at thisposition, and so that they are fastened alternately to differentsections of the chord. Other forms of shear connector can of course beused.

The particular preferred form of the deck material of this inventionillustrated by FIG. 1 comprises a relatively thin flat, uninterrupted,elongated, wiped-coat, galvanized steel strip 18 that when unrolled willlie flat along the surfaces 15 with its edge portions resting thereon.It is an important feature of this preferred form that the sheet metalused for the deck material is sufficiently thin that it will permitpre-rolling to roll form as illustrated. A plurality of elongated,rectangular closed cross-section duct members 19 are fastened at spacedintervals along the length of the strip, being disposed substantiallyparallel to each other. For convenience in description the top, bottomand side surfaces of the duct members are given the references 190, 19c,19b and 19d respectively. The members 19 are fastened to the strip byfastening means such that the bottom surface of each member is spaced asubstantial distance from the upper face of the strip 18 to provide aspace 20 for the entry of settable material between the duct members andthe strip.

In this particular embodiment the fastening means comprise a pluralityof Z-shaped members 21 having a flange 21a fastened, as by welding forexample, to the strip 18, while the other flange 21b is fastened, as bywelding for example, to the underface 190 of the respective duct member.The portion of each member 21 between the flanges is given the reference21c. In this embodiment owing to the presence of the shear connectormembers 16 the width of the strip is less than the length of each ductmember in the same direction, so that the ends of the duct membersprotrude beyond the edge portions of the strip, the amount of thisprotrusion being such that, as seen in FIG. I, the immediately adjacentregistering ends of two duct members of adjacent pieces of strip deckmaterial almost abut one another, so as to form a substantiallycontinuous duct. In other embodiments the width of the strip maycorrespond more exactly with the length of the duct members.

A roll of the preformed flexible strip deck material can be hoisted intoposition at the ends of two adjacent joists l3 and is deposited on themembers with the longitudinal axis of the roll transverse to the joistsand par allel to the primary members 12. The spacing between the joistsis predetermined to correspond to the width of the strip 18, so that itstwo edge portions reston the surfaces 15. Once accurately placed inposition the material can be unrolled. as indicated by the arrow 22,simply by pushing by hand in the direction of the arrow 23. Preferably,the length of the roll is the same as that of the joists, so that only asingle roll is required. With an unusually long span two rolls may beunrolled from opposite ends, the abutting ends being joined together, sothat the carriage of decking units within the building structure isavoided. Adjacent strips are adjusted longitudinally the very smallamount that is required to ensure that the duct members are accuratelyin register with one another and connectors, such as strips of suitableadhesive tape, may be applied around the closely adjacent ends to ensurethat wet concrete cannot enter.

The construction of the reinforced structure is now completed byapplying the usual upper wire mesh reinforcement 24 (see FIGS. I0 and11) and pouring a concrete slab 25 to the required thickness, the strip18 providing the necessary formwork. In some constructions it may bepossible to eliminate the wire mesh reinforcement, for example when thefasteners are continuous and can perform the function of the mesh. Theclose engagement of the flat surfaces of the edge portions of the sheetand the joists ensure that the concrete cannot leak between them whilein flowable condition. It is essential in pouring the slab that care betaken to completely fill the spaces 20, without the presence of voidstherein, and techniques required for this purpose are well known topersons silled in the particular art.

It will be noted particularly that at least one shearresistingconnecting fastening means 21 is interposed between each end of eachduct member 19 which extends over the joist surfaces and the portion ofthe strip 18 that is resting on and is fully supported by the joistsurfaces 15. The duct members thereby act as beams suporting via theconnecting members the part of the strip that extends between thesupport surfaces 15. They thereby act as shear and beam supports for thedead load of the wet concrete while it is being poured and forconstruction loads during the pouring. The action of the interveningconnecting members 21 is therefore to support the steel sheet in itssuspension from the duct member acting as a beam over substantially itsentire width at a large number of points, so that a relatively thinsheet (e.g. 0.030 inch for a slab of 5 inches overall thickness) can beused. The duct members provide a solid working plateform which can bewalked upon by workmen if necessary till the concrete is poured, andalso provide support for the reinforcing mesh 24 if used.

The duct members and the fastening connecting members are completelyencased with concrete, as described above, and will bond to the concreteas it cures. The connecting means must in themselves have sufficientshear resistance to transmit the corresponding forces between the ductmembers and the sheet and permit the desired composite action to beobtained. if desired, additional mechanical connecting means, such asprotruding lugs, depressions and ridges may be provided to ensuresufficient bonding. Such mechanical means will also increase thestiffness of the duct members. The mechanical action of the concreteencasing the duct members and connecting means, combined with the bondthat is developed between the two materials results in a compositestructural unit. The composite bond action between the concrete and therigid duct members will resist transverse shrinkage stresses during thecuring of the concrete, while longitudinal shrinkage stresses areresisted by the transfer of these stresses by the duct members to thebottom sheet. Once the concrete slab has been set the flat uninterruptedsheet constitutes the positive moment main reinforcement for the slab,carrying the tensile forces therein to the supporting joists, because ofits continuous unbroken form it can also act in the longitudinaldirection as an exceptionally effective temperature reinforcement forthe slat. Moreover, again because of its uninterrupted form itdistributes point load forces, caused for example by the movement of aheavy weight over the floor, over the slab and prevents cracking due tosuch forces.

Since the duct members are completely encased by the concrete the fullthickness of the floor slab may be considered in determining thecomposite action of the floor slab with the supporting members, and notonly the part of the slab that is above the ducts, as with theconstructions referred to above, as disclosed in U.S. Pat. No. 2,131,652and British Pat. No. 748,104.

Thus, there is a transfer of compressive stresses around the voidconstituted by the duct member due to its location within the body ofthe slab. This increases the effective thickness of the concrete andresults in an increase in the effective area for consideration indetermining the composite action. There is a consequential lowering ofthe centroidal axis of the composite section, with a correspondingincrease in the section modulus of the bottom of the supporting member,giving an overall decrease in steel stresses and greater stiffness,resulting in less deflection and less vibration. This may be contrastedwith the conventional prior art deck described above, which permits onlythe concrete over the metal deck to be considered in determining theextent of this composite action. Such conventional deck required thatthe shear connectors extend above the top of the deck, which results inthe development of a moment between the top of the supporting member andthe effective concrete, causing the cells of concrete formed by thistype of deck to rotate under the load.

The location of a layer of concrete under the duct members preventsuplift of the concrete slab away from the deck, the mechanical actionbetween the concrete and the fastening members, the bottom sheet and theduct members transferring the tension stresses between the latter twowhich therefore both act as positive reinforcements.

For convenience in terminology the term duct member alone is used in theclaims, and it will be understood by those skilled in the art that suchterm includes, pipes, tubes, and like members.

In the embodiment particularly described and shown the duct members areintended for electrical service, and therefore are shown as ofconventional closed rectangular transverse cross-section, sincesupplementary equipment for use with such ducts are readily commerciallyavailable. However, other closed cross-sections may also be used, suchas round or square tube. It is found that the improvements inperformance to be obtained by use of the new deck material are such thatit is also preferred to use duct members that are not necessarilyrequired to act for the carriage of services. Such non-service ductmembers may be of same or similar configurations, but the gauge of metalmay be reduced substantially. Different materials may also be used.

A duct member intended for electrical service must usually be of aminimum thickness specified by local regulations, and it is thereforecontemplated that deck material may be provided in which different typesof duct members are provided along the length thereof in order toachieve maximum flexibility and/or economy of material. Thus, it may bearranged that only each third or fourth duct member is particularlysuitable for electrical service, while the intervening members are ofsubstantially reduced thickness and/or cross-section. It is alsocontemplated that different duct members may be provided, depending upontheir specific function, for example, they may be successive groups offour, one of which is for electrical service, another is for telephone,a third is available for air conditioning service, and the remainingmember is for water, gas, or some other type of service.

It is also therefore a particularly useful feature that the design ofthe duct members is independent of the design of the bottom sheet. Thismay be contrasted with the conventional deck wherein the bottom sheet ispart of the duct member and must usually be of minimum thickness,greater than would otherwise be required, to meet the associatedregulations This blending of the duct members is possible in the shoprather than in the field and may be contrasted with a conventional deckwherein comparable very limited blending can only be obtained byalternating the use of electrical type and a non-electrical type deckmaterial.

In a particular preferred embodiment where all of the duct members aresuitable for electrical service the strip deck material is 4 or 5 feetwide and the duct members are each of 6 inches width and may be from 1/2 to 3 inches in height, in increments of one-half inch, the heightchosen being dependent upon the span of the deck material, the spacingof the duct members and the load on the deck during construction. Theduct members may be 12 inches, 15 inches or inches from one another. Thelower surface of the duct members will usually be spaced about lk inchesto 2 inches from the upper surface of the sheet metal strip 18.

Since the service ducts are completely encased in concrete material theyare protected from all sides, and this may be contrasted with the priorart deck materials described, in which only a light gauge sheet metallayer separates the duct from the floor area or ceiling space. The layerof concrete provided by the deck material of this invention in the space20 provides greater protection from fire, the provision of voids withinthe slab also acting to insulate the slab more effectively against thetransfer of heat through it. Therefore the fire rating of the structureis greater, or conversely the same fire rating is obtainable with asmaller overall floor thickness. This greater protection results in lessdamage in the event of small localized fires, and also decreases thepossibility of transfer of damage to other areas within the building.For the same reason sound transmission is reduced.

The width of the sheet 18 is made such in relation to the spacing of thejoists, and to the disposition of the connectors 16, that the edges ofthe sheet can be spaced from the connector members to ensure that theyare completely embedded in the concrete slab by means of anuninterrupted strip of concrete which surrounds them. This arrangementis important to ensure that the connector members and the deck materialdo not interact to apply torsional forces that can crack the concretedeck.

Since the deck material is unrolled it is important that the connectors16 be accurately located transversely of the joists 13, so that anunobstructed path is left for the unrolling, and this can readily beachieved by the use of jigs in the pre-attaching operation. it is alsoimportant that the duct members be accurately located along the lengthof the strip so that adequate registration of adjacent members isobtained. As the deck is unrolled the edge portions thereof resting onthe joists may be fastened thereto, for example by spot welding orsuitable clips. in some floor constructions it may not be necessary toprovide shear connectors, for example the above-mentioned welding of thedeck to the beam members providing sufficient shear horizontalresistance.

Another application of the strip deck material of the invention is inbridge construction to provide permanent formwork and reinforcing forthe bridge slab. In this application the duct and fastening connectingmembers would be larger and heavier due to longer spans and heavierloads. Also, the bottom sheet would be heavier and could be either flator corrugated for increased strength and stiffness. The connectingmembers for each duct may, for example, comprise a longitudinal webfastened at its upper edge to the underside of the duct while its loweredge is fastened to the strip, shear-resisting cross-webs also beingprovided at intervals transverse to the longitudinal webs and shaped tofit around the duct periphery. The cross and longitudinal webs arejoined together at their junctions; the cross webs are also fastened tothe duct and to the strip as required in order to provide the necessaryhorizontal shear resistance. The duct members create large voids withinthe slab thereby reducing the dead load of the slab. Once the concretehas set, composite action between the concrete and deck is achievedthrough the mechanical action of the concrete and the shearresistingconnecting members and also through the chemical bond developed betweenthe concrete and duct members, connecting members and bottom sheet.

The embodiment of FIG. 2 differs from that of FIG. 1 only in that theduct members 19 are continuous over a plurality of elongated stripsdisposed side by side and also continuous over a plurality of supportsurfaces 15. Thus at least two strips are disposed with the direction ofelongation parallel to one another, while each duct member is of alength such as to extend uninterruptedly over all of the strips.Nevertheless such a structure can readily be rolled as shown, and easilyunrolled when once hoisted into position on the support structure. Theimmediately adjacent edges of each adjacent two strips are spaced fromone another to clear the shear connectors 16. With a deck material inaccordance with the invention it is possible, for example, to provide asmany as six strips side by side, each strip being of width 5 feet and oflength 40 feet, so that an area of approximately 1,200 sq. ft. can beapplied as a single roll.

Various shapes and types of fastening means 21 may be employed forconnecting each duct member 19 to the strip 18 with the undersurface 19cor its equivalent spaced from the adjacent strip surface, so as toprovide the space 20 therebetween, and some examples only are shown inFIGS. 3-11. Preferably the concrete extends completely under the ductmembers but an equivalent action can be obtained if the space 20 permitsonly partial interposition thereof, the minimum required for beneficialaction to be obtained being readily calculable by those skilled in theart.

Generally the fastening means members should have a truss-like orsuspended configuration and be capable of transferring horizontalstresses between the duct member, metal strip and the concrete, afterthe concrete is poured and set. Moreover they should provide adequatelateral stability to the duct member, so that they will readilywithstand the construction loads, workmen walking on them, and the loadof the wet concrete applied thereto while the floor slab is beingpoured. The members may be mechanically deformed in shape or otherwiseprovided with means which mechanically increase the bond with theconcrete. Such bonding action combined with the mechanical action of theconcrete completely encasing these members enables full transfer of thestresses between the duct members, bottom sheet and the concrete.

In the embodiment illustrated by FIG. 3 the fastening member 21 is ofwhat is called zig-zag configuration and is fastened adjacent thevalleys 21a thereof to the metal strip, while the peaks 21b thereof arefastened to the underside 190 of the rectangular-configuration ductmember. It will be noted particularly that at the ends of the supportmember a vertically extending portion 21d is provided, in order toensure full transfer of the forces applied to the duct member I9 to theedge portions of the strip that are fully supported by the joists 13.

In the embodiment of FIG. 4 the support member for each duct membercomprises two zig-zag shaped rods disposed one on each side of therespective duct member, the valleys being fastened to the sheet 18,while the crests are fastened to the side walls 19b and I9d. Verticalend portions 21d are also provided. These rods may be deformed toincrease their bond with the surrounding concrete.

In general the specific shape, arrangement and disposition of thefastening members will be determined by factors such as economy ofmaterial, ease of fabrication of the members and ease and economy infastening them accurately and securely in position.

In the embodiment of FIG. 5 the fastening members comprise a pluralityof U-shaped brackets having flanges 21a and 21b facing the same way, theupper flanges 2112 being fastened to the flat underface 19c, while thelower flange 21a is fastened to the strip.

In the embodiment of FIGS. 6 and 7 the members may comprise Z-shapedbrackets as shown in solid lines. Instead they may comprise brackets ofso-called top-hat" shape as shown in the combination of solid and brokenlines, the brim" members 210 being fastened to the strip 18, while thehat top" 21b is fastened to the face 19d. Similarly, in the embodimentsof FIGS. 8 and 9 the support members may be of L-shape, as shown insolid lines, or instead of deep top-hat" cross-section, as indicated bythe solid and broken lines, in this case the hat-top 21b being fastenedto the face 19a.

FIG. 10 shows the connecting means of FIGS. 1 and 2, and shows also theupper reinforcement mesh 24 and the complete cement slab 25. In theembodiment of FIG. 11 each bracket member 21 is of greater width in thedirection of elongation of the strip at the junction of the flange 21aand the body 21c than at the junction of the flange 21b and body 210,such a construction making for easier access in fastening and alsoproviding increased transverse stability. The unsupported span of thebottom strip between the duct members also is reduced.

In the preferred example of FIGS. 12 and 13 the sections of deckmaterial are of flat form and are placed on the joist surfaces 15 withthe length of the strip 18 parallel to the length of the duct members 19and transverse to the length of the joists 13. In the particularembodiment illustrated the strip is of sufficient length to extendcontinuously over several spans, and the duct members also arecontinuous and extend over the same number of spans. A complete floor isassembled by laying several assembled sections side by side with theiradjacent edges 18a abutting one another; these abutting edges may beturned upward as illustrated and arranged to interlock with one anotheror to be crimped together in any suitable known manner along theirlength. As illustrated by FIG. 13 the duct members may have at least thefaces 19a and 1% longitudinally corrugated to increase theirlongitudinal rigidity.

The fastening means of this embodiment also are Z- shaped members, aswith the embodiments of FIGS. 1, 2, IO and 11, but each is of sufficientlength to extend the full width of the strip, and therefore acts tofasten more than one duct member (three in this embodiment) to the strip18. In other embodiments only some of these members may be continuousacross the strip. As with the other embodiments care is taken to ensurethat fastening members are interposed between each duct and theunderlying portions of the strip 18 that are resting on the joistsurfaces 15, and in this embodiment these are illustrated as being ofthe top-hat shape described with reference to FIG. 7. Subsequent tomounting the sections on the joists the feet of these top-hat fasteningmembers are welded through the strip 18 to the joist surfaces, so thatthey act as integral shear connectors, avoiding the need to provide thespecial separate connectors 16 of the previously described embodimentsand thereby considerably simplifying the assembly and decreasing itscost. This feature can also be used with the other embodiments of theinvention.

At the present time sheet steel is readily available in widths of onlyabout 5-6 feet, so that the fabrication of a coil having a width of say15 feet would involve preedge welding together three separate strips.With the construction of FIG. 12 separate strips of up to about 45 feetlength and 56 feet wide can easily be provided, the duct members 19holding the strip flat in the longitudinal direction, and the continuousfastening members 21 at least assisting in holding it flat in thetransverse direction, to permit easy handling. It will be noted thateach strip is of substantially the width of the steel strip available,less the small amount required for the narrow upturned edges 18a, thatis to say nearly 5-6 feet, whereas the loss in width caused by rollingto provide the prior art corrugated sections results in strips that areonly about 2-3 feet wide. The welded wire mesh used in prior artcorrugated constructions is not needed except perhaps at joints ofadjacent sections of deck.

The deck of this invention may be produced in a relatively smallmanufacturing area with relatively inexpensive equipment, such as spotwelding equipment, unlike the conventional prior art deck describedwhich requires large manufacturing areas and expensive roll formingequipment. For example, the sheet steel can be supplied in rolls whichare unrolled at a specific location at which the duct members areinstalled, and then immediately stacked or recoiled into compact form toawait transportation to and installation on the site. Any length of deckcan be provided, depending on the length of completed strip or thediameter of the roll that can be handled efficiently. For example, asection of deck 40 feet long can be rolled into a coil having a diameterof 4-5 feet.

I claim:

I. A reinforced structure comprising:

a. a support structure providing two spaced support surfaces,

b. a plurality of parallel, spaced, elongated, loadbearing duct membersof closed cross-section extending between the said spaced supportsurfaces and over at least a portion of each of the said surfaces,

c. shear-resisting connecting means disposed between each supportsurface and the respective portion of each duct member extendingthereover, whereby each duct member constitutes a beam member supportedby the support surfaces,

d. void-free shear-resisting connecting means connected to the ductmembers between the said portions which extend over the surfaces,

e. a thin continuous strip extending beneath and spaced from the ductmembers over the space between the spaced support surfaces, andconnected to the last-mentioned connecting means to be supported fromthe duct member to constitute formwork for a superimposed layer ofsettable material and reinforcement for the layer when set,

f. and a void-free layer of set, settable material that has been set onthe strip as formwork therefor. the layer enclosing the duct memberswhich thereby act as reinforcement for the layer when set, the layeralso enclosing the connecting means and tilling the spaces between thestrip and the undersides of the duct members.

2. A structure as claimed in claim 1, wherein the firstmentionedconnecting means are disposed at the edges of the respective strip andare fastened to the duct members and the strip.

3. A structure as claimed in claim 1, wherein the said thin strip is ofsufficient longitudinal flexibility to be rolled into the form of a rollhaving a longitudinal roll axis, the duct members being disposed withtheir respective directions of elongation parallel to the said rollaxis.

4. A structure as claimed in claim 3, comprising at least two elongatedthin strips disposed with their directions of elongation parallel to oneanother, each duct member being of a length to extend uninterruptedlyover all of the strips.

5. A structure as claimed in claim 1, wherein the ends of each ductmember extend beyond the immediately adjacent edges of the strip.

6. A structure as claimed in claim 1, wherein the strip is of elongatedform, the duct members are disposed with their directions of elongationparallel to the direction of elongation of the strip, and at least oneof the connecting means extends continuously across the width of thestrip to connect a plurality of the duct members to the strip.

7. A structure as claimed in claim 1, wherein the connecting meansconnecting each duct to the strip comprise at least one member ofzig-zag configuration fastened adjacent the valleys thereof to the stripand adjacent the peaks thereof to the respective duct member.

8. A structure as claimed in claim 7, wherein the said zig-zagconnecting means comprise at least one bent thin sheet member interposedbetween the sheet and the respective duct member.

9. A structure as claimed in claim 1, wherein the said connecting meanscomprise a plurality of spaced members of top-hat cross-section havingthe brim members fastened to the strip and the hat top fastened to theduct member.

10. A structure as claimed in claim 1, wherein the said connecting meanscomprise a plurality of spaced bracket members interposed between thestrip and the respective duct member and fastened thereto.

11. A structure as claimed in claim 10, wherein each bracket member isof greater width in the direction of elongation of the strip at itsjunction with the strip than at its junction with the respective ductmember.

12. A structure as claimed in claim 1, wherein the duct members arelongitudinally corrugated to increase the longitudinal rigidity thereof.

1. A reinforced structure comprising: a. a support structure providingtwo spaced support surfaces, b. a plurality of parallel, spaced,elongated, load-bearing duct members of closed cross-section extendingbetween the said spaced support surfaces and over at least a portion ofeach of the said surfaces, c. shear-resisting connecting means disposedbetween each support surface and the respective portion of each ductmember extending thereover, whereby each duct member constitutes a beammember supported by the support surfaces, d. void-free shear-resistingconnecting means connected to the duct members between the said portionswhich extend over the surfaces, e. a thin continuous strip extendingbeneath and spaced from the duct members over the space between thespaced support surfaces, and connected to the last-mentioned connectingmeans to be supported from the duct member to constitute formwork for asuperimposed layer of settable material and reinforcement for the layerwhen set, f. and a void-free layer of set, settable material that hasbeen set on the strip as formwork therefor, the layer enclosing the ductmembers which thereby act as reinforcement for the layer when set, thelayer also enclosing the connecting means and filling the spaces betweenthe strip and the undersides of the duct members.
 2. A structure asclaimed in claim 1, wherein the first-mentioned connecting means aredisposed at the edges of the respective strip and are fastened to theduct members and the strip.
 3. A structure as claimed in claim 1,wherein the said thin strip is of sufficient longitudinal flexibility tobe rolled into the form of a roll having a longitudinal roll axis, theduct members being disposed with their respective directions ofelongation parallel to the said roll axis.
 4. A structure as claimed inclaim 3, comprising at least two elongated thin strips disposed withtheir directions of elongation parallel to one another, each duct memberbeing of a length to extend uninterruptedly over all of the strips.
 5. Astructure as claimed in claim 1, wherein the ends of each duct memberextend beyond the immediately adjacent edges of the strip.
 6. Astructure as claimed in claim 1, wherein the strip is of elongated form,the duct members are disposed with their directions of elongationparallel to the direction of elongation of the strip, and at least oneof the connecting means extends continuously across the width of thestrip to connect a plurality of the duct members to the strip.
 7. Astructure as claimed in claim 1, wherein the connecting means connectingeach duct to the strip comprise at least one member of zig-zagconfiguration fastened adjacent the valleys thereof to the strip andadjacent the peaks thereof to the respective duct member.
 8. A structureas claimed in claim 7, wherein the said zig-zag connecting meanscomprise at least one bent thin sheet member interposed between thesheet and the respective duct member.
 9. A structure as claimed in claim1, wherein the said connecting means comprise a plurality of spacedmembers of top-hat cross-section having the brim members fastened to thestrip and the hat top fastened to the duct member.
 10. A structure asclaimed in claim 1, wherein the said connecting means comprise aplurality of spaced bracket members interposed between the strip and therespective duct member and fastened thereto.
 11. A structure as claimedin claim 10, wherein each bracket member is of greater width in thedirection of elongation of the strip at its junction with the strip thanat its junction with the respective duct member.
 12. A structure asclaimed in claim 1, wherein the duct members are longitudinallycorrugated to increase the longitudinal rigidity thereof.